Capturing carbon dioxide

ABSTRACT

Techniques for drift elimination in a liquid-gas contactor system include configuring a pre-fabricated mechanical frame coupled to a drift eliminator material to produce a framed drift eliminator assembly with substantially no air gaps between the drift eliminator material and the pre-fabricated mechanical frame, and coupling the framed drift eliminator assembly to the liquid-gas contactor system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of and claims priority toU.S. application Ser. No. 15/622,883, filed on Jun. 14, 2017, whichclaims priority to U.S. patent application Ser. No. 62/349,883, entitled“Capturing Carbon Dioxide” and filed on Jun. 14, 2016, the entirecontents of which are incorporated by reference herein.

TECHNICAL FIELD

This disclosure describes systems, apparatus, and methods for gas-liquidcontacting for the recovery of carbon dioxide from gases.

BACKGROUND

Gas-liquid contact systems include systems used for capture of carbondioxide (CO₂) from concentrated (for example, point source) gas streams,such as CO₂ produced from industrial sources (for example, power plants,concrete plants, flue stacks), as well as CO₂ captured directly fromdilute sources, for example ambient air.

SUMMARY

In an example implementation, a method for distributing a liquid in aliquid-gas system includes flowing a liquid into a system of nozzles andbasin of the liquid-gas contacting system; and operating the nozzles andbasin system with a distribution sub-assembly configured to operate thenozzles under a plurality of liquid flow rates and maintaining aconsistent spatial liquid distribution of the liquid within thedistribution sub-assembly at the plurality of liquid flow rates.

In an aspect combinable with the example implementation, thedistribution sub-assembly includes a first portion of nozzles having afirst intake height and a second portion of nozzles having a secondintake height shorter than the first intake height.

In another aspect combinable with any of the previous aspects, thenozzle and basin system configured to hold a plurality of liquid levelsand at least a portion of the first portion of nozzles and the secondportion of nozzles activate within the plurality of liquid levels.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles and the second portion of nozzles are distributedwithin the basin.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles are paired with the second portion of nozzles and thepairs are distributed within the basin.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles are distributed within a center portion of the basinand the second portion of nozzles are distributed evenly within thebasin.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles are distributed within a portion of the basinfurthest from the liquid inlet of the basin.

In another aspect combinable with any of the previous aspects, theplurality of liquid flow rates includes at least one of a flush flowrate or a pulse flow rate, and the flush flow rate produces a particularliquid level that activates at least the first portion of nozzles, andthe pulse flow produces another particular liquid level that activatesat least the second portion of nozzles.

In another aspect combinable with any of the previous aspects, flowingthe liquid through at least some of the first portion of nozzles orsecond portion of nozzles, and flowing the liquid from the nozzles to aportion of packing material of the liquid-gas contactor system of up toabout 7 litres per second per square meter of packing material.

In another aspect combinable with any of the previous aspects, the pulseflow is 10 percent of the flush flow.

In another aspect combinable with any of the previous aspects, at leasta portion of the first and second nozzles are configured to activatewithin the plurality of liquid flow rates to produce overlapping spraycones.

In another aspect combinable with any of the previous aspects, themethod for gas-liquid contacting includes capturing CO₂ from at leastone of a dilute gas source or point source with the liquid-gas contactorsystem.

In another aspect combinable with any of the previous aspects, thedilute gas source includes air, and the point source includes at leastone of flue gas, reservoir gas, exhaust flue stack gases from powergeneration processes, exhaust flue stack gases from concrete productionprocesses, or exhaust from combustion processes.

In another aspect combinable with any of the previous aspects, theliquid-gas contacting system is operated as part of a cooling watersystem.

In another example implementation, a method of solids separation in aliquid-gas contacting system includes operating a basin collectionsystem fluidly coupled to a mechanical removal system and at least onesolid collection zone, flowing a mixed stream of liquids and solids intothe basin collection system of the liquid-gas contacting system, andcollecting and processing the solids from the mixed stream with themechanical removal system and the at least one solid collection zone.

In an aspect combinable with the example implementation, the mechanicalremoval system includes at least one of an auger, screw conveyor,progressive cavity pump, screw pump, high density solids pump,reciprocating pump.

In another aspect combinable with any of the previous aspects, the basincollection system is non-circular or rectangular in shape.

In another aspect combinable with any of the previous aspects, the basincollection system includes an inclined bottom basin area and a liquidlevel; and a substantial portion of the inclined bottom basin area isconfigured above the liquid level and sloped down towards the at leastone solid collection zone.

In another aspect combinable with any of the previous aspects, furtherincluding capturing CO₂ from at least one of a dilute gas source orpoint source with the liquid-gas contactor system.

In another aspect combinable with any of the previous aspects, thedilute gas source includes air and the point source includes at leastone of flue gas, reservoir gas, exhaust flue stack gases from powergeneration processes, exhaust flue stack gases from concrete productionprocesses, and exhaust from combustion processes.

In another aspect combinable with any of the previous aspects, theliquid-gas contacting system is operated as part of a cooling watersystem.

In another example implementation of a method of drift elimination in aliquid-gas contacting system, a pre-fabricated mechanical frame isconfigured and coupled to a drift eliminator material to produce acombined framed drift eliminator assembly with substantially no air gapsbetween the drift eliminator material and mechanical frame, and couplingthe pre-fabricated framed drift eliminator to the liquid-gas contactingsystem.

In another aspect combinable with any of the previous aspects, theframed drift eliminator assembly includes a flexible sealant coupled tothe drift eliminator material.

In another aspect combinable with any of the previous aspects, theliquid-gas contactor system includes capturing CO₂ from at least one ofa dilute gas source or point source with the liquid-gas contactorsystem.

In another aspect combinable with any of the previous aspects, thedilute source includes air and the point source includes one or more offlue gas, reservoir gas, exhaust flue stack gases from power generationprocesses, exhaust flue stack gases from concrete production processes,and exhaust from combustion processes.

In another aspect combinable with any of the previous aspects, theliquid-gas contacting system is operated as part of a cooling watersystem.

In another example implementation, a nozzle and basin apparatus for usein a liquid-gas contacting system includes a liquid inlet port coupledto a system of nozzles and basin, and a distribution sub-assemblycoupled to the nozzle and basin system configured to operate under aplurality of liquid flow rates while maintaining consistent spatialliquid distribution.

In an aspect combinable with the example implementation, thedistribution sub-assembly includes a first portion of nozzles having afirst intake height and a second portion of nozzles having a secondintake height shorter than the first intake height.

In another aspect combinable with any of the previous aspects, thenozzle and basin system is configured to accommodate a plurality ofliquid levels.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles and the second portion of nozzles are distributedwithin the basin.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles are paired with the second portion of nozzles and thepairs are distributed as sets within the basin.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles are distributed within a center portion of the basinand the second portion of nozzles are evenly distributed within thebasin.

In another aspect combinable with any of the previous aspects, the firstportion of nozzles distributed within the portion of the basin locatedopposite to a liquid inlet port.

In another aspect combinable with any of the previous aspects, theplurality of liquid flow rates includes at least one of a flush flowrate or a pulse flow rate, and at least the first portion of nozzles areconfigured to activate during the flush flow rate, and at least thesecond portion of nozzles are configured to activate during the pulseflow rate.

In another aspect combinable with any of the previous aspects, thedistribution sub-assembly is fluidly coupled to at least a portion ofpacking material of the liquid-gas contactor system, and at least aportion of the first and second nozzles configured to distribute aliquid flow to the packing material of up to 7 litres per second persquare meter of packing material.

In another aspect combinable with any of the previous aspects, pulseflow rates are 10 percent of flush flow rates.

In another aspect combinable with any of the previous aspects, thedistribution sub-assembly includes a first quantity of the first portionof nozzles and a second quantity of the second portion of nozzles.

In another aspect combinable with any of the previous aspects, both thefirst and second quantities of the respective first and second portionsof nozzles are evenly distributed within a complete surface area of abasin of the nozzle and basin system.

In another aspect combinable with any of the previous aspects, a centerarea of a basin of the nozzle and basin system includes a first densityof the first portion of nozzles and a perimeter area of the basinincludes a second density of the first portion of nozzles less than thefirst density.

In another aspect combinable with any of the previous aspects, thecenter area of the basin of the nozzle and basin system includes a firstdensity of the second portion of nozzles and the perimeter area of thebasin includes a second density of the second portion of nozzles greaterthan the first density.

In another aspect combinable with any of the previous aspects, an areaof a basin of the nozzle and basin system adjacent to a liquid inletport of the system includes a first density of the first portion ofnozzles and a portion of the basin not adjacent the liquid inlet portincludes a second density of the first portion of nozzles less than thefirst density.

In another aspect combinable with any of the previous aspects, theliquid-gas contactor is configured for capturing CO₂ from at least oneof a dilute gas source or a point source.

In another aspect combinable with any of the previous aspects, thedilute source includes air and the point source includes one or more offlue gas, reservoir gas, exhaust flue stack gases from power generationprocesses, exhaust flue stack gases from concrete production processes,and exhaust from combustion processes.

In another aspect combinable with any of the previous aspects, theliquid-gas contactor system is configured as part of a cooling watersystem.

In another example implementation, a liquid-gas contacting apparatusincludes a basin collection system fluidly coupled to at least one ormore solid collection zones, and a solids transfer system coupled to thebasin collection system configured to remove solid material from the atleast one or more solid collection zones.

In another aspect combinable with any of the previous aspects, thesolids transfer system includes at least one of an auger, screwconveyor, progressive cavity pump, screw pump, high density solids pump,reciprocating pump.

In another aspect combinable with any of the previous aspects, the basincollection system is non-circular, or rectangular in shape.

In another aspect combinable with any of the previous aspects, the basincollection system includes an inclined bottom basin area and a liquidlevel; and the inclined bottom basin area is sloped down towards the atleast one or more collection zones.

In another aspect combinable with any of the previous aspects, theliquid-gas contactor apparatus is configured to capture CO₂ from one ormore of a dilute gas source or a point source

In another aspect combinable with any of the previous aspects, thedilute source includes air and the point source includes one or more offlue gas, reservoir gas, exhaust flue stack gases from power generationprocesses, exhaust flue stack gases from concrete production processes,and exhaust from combustion processes.

In another aspect combinable with any of the previous aspects, theliquid-gas contacting system is operated as part of a cooling watersystem.

In another example implementation, the liquid-gas contacting apparatusincludes a pre-fabricated mechanical frame and drift eliminator materialcoupled to the pre-fabricated mechanical frame to form a framed drifteliminator assembly.

In another aspect combinable with any of the previous aspects, theframed drift eliminator assembly includes flexible sealant pressedagainst the drift eliminator material configured for substantially noair gaps.

In another aspect combinable with any of the previous aspects, theliquid-gas contacting apparatus is configured for capturing CO₂ from oneor more of a dilute source or point source.

In another aspect combinable with any of the previous aspects, thedilute source includes air and the point source includes one or more offlue gas, reservoir gas, exhaust flue stack gases from power productionequipment, exhaust flue stack gases from concrete production equipment,and exhaust from combustion equipment.

In another aspect combinable with any of the previous aspects, theliquid-gas contacting system is operated as part of a cooling watersystem.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustrative nozzle and basin system for distributionof liquid flow through both pulse and flush flow regimes of a liquid-gascontactor system.

FIG. 2A is a graph illustrating the liquid-gas contactor system flushflow and pulse flow rates versus time.

FIG. 2B is a graph illustrating liquid flow dampening effects over timefor a liquid-gas contactor system with top basin liquid distributiontechnology.

FIG. 3 depicts an illustrative collection basin and solids removal unitof a liquid-gas contactor system.

FIG. 4 depicts an illustrative structural harness and drift eliminatorassembly of a liquid-gas contactor system.

FIG. 5 depicts an illustrative structural harness and drift eliminatorassembly with flexible sealant flaps of a liquid-gas contactor system.

FIG. 6 depicts an illustrative elevation view of an embodiment of adrift eliminator and sealant configuration fitted in front of the fancowling of a liquid-gas contactor system.

FIG. 7 depicts an illustrative plan view of an embodiment of a drifteliminator and sealant configuration fitted in front of a fan cowling ofa liquid-gas contactor system.

FIG. 8 depicts an illustrative elevation view of an embodiment of adrift eliminator and sealant configuration fitted between the packingmaterial, overall housing and fan plenum area of a liquid-gas contactorsystem.

FIG. 9 depicts an illustrative plan view of an embodiment of a drifteliminator and sealant configuration fitted between the packingmaterial, overall housing and fan plenum area of a liquid-gas contactorsystem.

FIG. 10 depicts an illustrative view of a liquid-gas contactor slabconfiguration.

FIG. 11 depicts an illustrative system for capturing carbon dioxide fromdilute sources, including a liquid-gas contactor system.

DETAILED DESCRIPTION

A number of innovations to existing cooling tower components are neededto tailor them, and the system overall, to improve the safety,performance, and cost of application in a liquid-gas contactor systemfor CO₂ capture. The CO₂ capture may apply to point sources, for exampleflue exhaust gas from combustion equipment, flue exhaust gas from powerplants or cement plants and the like, and also to dilute sources, forexample atmospheric CO₂. These innovations may also improve performancefor cooling water applications.

A set of nozzles and basins is described, with desirable features thataccommodate a large range of liquid flow rates while maintainingconsistent spatial liquid distribution.

A basin configuration is described, that promotes liquid collection andflow patterns within, such that suspended solids are able to settle outand migrate to one or more collection zones for removal.

Embodiments of a mechanical frame containing drift eliminator materialare described, wherein the frame's shape and method of installationprevents air bypass around the drift eliminator material.

Multiple configurations of sealing are described, wherein the sealantlocation and method of application prevents air bypass around the drifteliminator material.

The features described here offer technical and commercial advantagesabove what the existing systems and methods provide. For example,conventional nozzle and basin systems are based on liquid distributionnozzles used in the hot water basin of cooling towers or thedistribution basin of crossflow air contactors. Normally these nozzlesare all similar in geometry and are all inserted into holes in a basinmounted above the packing material or are part of splash bars. Whenfluid is fed into the top basin, the fluid flows through the entirebasin and builds up a liquid static head, which in turn supplies thepressure required to drive the fluid through the nozzles and generatethe spray cone pattern. The liquid depth in these basins is generallyquite low, for example they may be on the order of 10 to 30 centimeters.These nozzles have a certain range of liquid static head, across whichthey can produce an acceptable spray pattern. They are designed tooperate at a single fixed flow rate of liquid to the basin. If operatedat a lower flow rate, these existing systems will not build up theappropriate static head, which will not produce a full “nozzle spraycone” and as a result, they distribute liquid over a smaller areadirectly below the nozzle, leaving under-wetted zones of packingmaterial in between nozzles. The issue of under-wetted packing alsooccurs when the liquid flow to the basin is further reduced such thatsome areas of nozzles located far from the liquid entry point do notreceive any fluid. While under-wetted packing material may somewhatreduce performance in cooling towers due to the impact on heat exchangebetween air and liquid, it has other challenges when present in carbondioxide capture facilities. Under-wetted zones in packing material donot capture CO₂ as well as properly wetted packing material zones.Implementations of a nozzle and basin system disclosed here resolves theunder-wetted problem by configuring the nozzle and basin system suchthat only some of the nozzles are active at low liquid levels (and theassociated static head) in the basin, which correspond to low flow tothe basin, and other nozzles activate at higher liquid levels (andassociated higher static head) in the basin, corresponding to high flowto the basin. This way, at low flow, each active nozzle distributes ahigher flow rate than if all nozzles were active, enabling them toproduce a full spray cone, and to cumulatively supply liquid to theentire top surface area (footprint) of the packing under all flowconditions. This configuration delivers liquid flow evenly, produceseven spatial liquid distribution below the basin, and as a result,provides better wetting of the packing surface which in turn allows forgreater overall CO₂ capture from the gas that makes contact with theliquid. Consistent spatial liquid distribution, in some aspects, mayoccur where even distribution of liquid across the packing surface area,or square footage, is achieved.

As another example, if the process solution contains particulates orfines, and it flows over the gas-liquid contactor packing, the contactorpacking itself will work to disperse the fines over the entire area ofthe liquid collection basin located in an area underneath the packingmaterial. As the liquid drops fall out of the bottom of the packing, thesolids they contain may settle onto the liquid collection basin floorwhen the liquid flow is not sufficient to suspend and carry the finesalong the basin to the suction of the liquid discharge pump. Thus theliquid collection basin could act similar to a solids settling tank. Theliquid collection basin's large inclined section, located above liquidlevel, facilitates build-up of the solid layer. As drops fall and hitthis inclined section, they cause a “splash.” On a perfectly horizontalsurface this splash would cause the solids to jostle from one place toanother with no net movement in one single direction over long periodsof time. But with an inclined section as described in exampleimplementations in the present disclosure, the force of the droplethitting the inclined surface washes the solids down the incline. This isdue in part to the force of the droplet hitting the surface, as well asthe force of gravity pulling more solids in the downward direction.Thus, even with very small inclines, the solids will move toward thelower end of the surface and eventually discharge into a sump area wherethey may be removed, for example, with mechanical solids removalequipment including but not limited to an auger, screw conveyor,progressive cavity pump, screw pump, high density solids pump, orreciprocating pump, and the clarified liquid may also be withdrawn fromthe contactor liquid collection basin.

In another example, the drift eliminator installation and housingdescribed in implementations of the present disclosure may allowstandard drift eliminators to be mounted in a precisely machined framebefore the overall frame is installed on the air contactor or coolingtower structure. For example, this frame may be pre-fabricated at ashop, and then the frame may be shipped to the location of the coolingtower or air contactor. By installing the drift eliminator sheets into aprecisely machined frame, a tighter seal may be attained between sheetsand within the frame itself. The frame is then designed to be installedin the field, and fit over the walls that enclose the outlet of thegas-liquid contactor. This installation method in combination with thedesign of the frame to “fit over” the structure outlet, allows a tight,consistent seal of the drift eliminator perimeter to the outflow gas andallows higher performance control of drift.

In another example, drift eliminator installation and housing may beimproved in some applications by installing and sealing the drifteliminator material around the area immediately upstream of the fanhousing. This method of installing and housing drift eliminator materialcan be applied to configurations such as dual, or single cross flowinduced fan systems, where the area immediately upstream of the fancowling can be covered with drift eliminator material, and the drifteliminator material can be supported and sealed such that any air movingthrough the packing material cannot leave the system without firstmoving through the drift eliminator material. In these induced fansystems, the pressure gradient between the system and the outsideenvironment is such that gas will always leak into the system ratherthan out of the system, which also aids in preventing escape of liquidaerosols, also known as drift, from the system.

In another example, the drift eliminator material is positioned betweenthe packing material and gas outlet, where the drift eliminator materialmay be physically attached to the packing material and sealant is thenadditionally applied around the perimeter of the drift eliminatormaterial, sealing outer edges of the material to the outer housing ofthe gas contactor. Sealing the drift eliminator material to the housingwalls in this way provides a desirable seal against any gaps, forexample between the packing material and the housing, where gas and/orliquid may be able to move, that could allow for air entrained withliquid to bypass the drift eliminator material.

These modifications to the drift eliminator fabrication, installment andhousing/sealing may provide technical and commercial improvements to theCO₂ capture method/device, because the system includes chemicals thatmust be contained within the contactor with higher thresholds ofcontainment than those applied to cooling water systems; therefore,these embodiments are useful in the dilute source CO₂ capture field. Insome aspects these stringent methods of fabrication may not be necessaryfor industrial cooling units from a drift perspective, however, thesedesigns and methods may be more economical than the current method ofinstalling drift eliminators into cooling towers in the field.

Each of the configurations described later may include process streams(also called “streams”) within a system for capturing carbon dioxidefrom gaseous sources, including dilute sources such as the atmosphere.The process streams can be flowed using one or more flow control systemsimplemented throughout the system. A flow control system can include oneor more flow pumps to pump the process streams, one or more fans orblowers to move gaseous process streams, one or more flow pipes throughwhich the process streams are flowed and one or more valves to regulatethe flow of streams through the pipes.

In some implementations, a flow control system can be operated manually.For example, an operator can set a flow rate for each pump and set valveopen or close positions to regulate the flow of the process streamsthrough the pipes in the flow control system. Once the operator has setthe flow rates and the valve open or close positions for all flowcontrol systems distributed across the system for converting calciumoxide to calcium hydroxide, the flow control system can flow the streamsunder constant flow conditions, for example, constant volumetric rate orother flow conditions. To change the flow conditions, the operator canmanually operate the flow control system, for example, by changing thepump flow rate or the valve open or close position.

In some implementations, a flow control system can be operatedautomatically. For example, the flow control system can be connected toa computer or control system (e.g., control system 999) to operate theflow control system. The control system can include a computer-readablemedium storing instructions (such as flow control instructions and otherinstructions) executable by one or more processors to perform operations(such as flow control operations). An operator can set the flow ratesand the valve open or close positions for all flow control systemsdistributed across the facility using the control system. In suchimplementations, the operator can manually change the flow conditions byproviding inputs through the control system. Also, in suchimplementations, the control system can automatically (that is, withoutmanual intervention) control one or more of the flow control systems,for example, using feedback systems connected to the control system. Forexample, a sensor (such as a pressure sensor, temperature sensor orother sensor) can be connected to a pipe through which a process streamflows. The sensor can monitor and provide a flow condition (such as apressure, temperature, or other flow condition) of the process stream tothe control system. In response to the flow condition exceeding athreshold (such as a threshold pressure value, a threshold temperaturevalue, or other threshold value), the control system can automaticallyperform operations. For example, if the pressure or temperature in thepipe exceeds the threshold pressure value or the threshold temperaturevalue, respectively, the control system can provide a signal to the pumpto decrease a flow rate, a signal to open a valve to relieve thepressure, a signal to shut down process stream flow, or other signals.

Referring to FIG. 1, a basin and nozzles system for distributing liquidsolution over packing is described with respect to illustrative system100. Liquid solutions include, for example, water, sodium hydroxidesolution, potassium hydroxide solution, and the like. As depicted inFIG. 1, liquid stream 101 is provided to the basin and nozzles system100. In some aspects, this stream may be provided at in an intermittentflow pattern, e.g., it may flow at a first rate that is higher than atleast one second rate, to introduce pulses of flow to the basin andnozzle system. For example, stream 101 could be repeatedly switchingbetween flowing the fluid briefly at a very high rate, followed byshutting the stream off for a duration of time, then followed by flowingthe fluid briefly at a lower flow rate, and repeating versions of thiscycle. In another example, stream 101 could be repeatedly switchingbetween flowing the fluid briefly at a very high rate, followed by atleast one second, lower flow rate, and cycling between these flow ratesin a defined cycle over time.

In some embodiments, as a result of liquid stream 101 flowing into thebasin and nozzle system 100, the fluid builds up in the basin and nozzlesystem 100 until it reaches a certain static head level 106 that enablesflow through at least one of a first type of nozzle 103, such thatnozzles 103 become active. In some aspects, nozzles 103 have an intakeheight 105 within the basin which could enable proper flow and aspecific liquid spray cone geometry at or above the lower static liquidhead associated with liquid level 106. The intake height 105 could beflush with the basin, or the intake height 105 could be some distanceabove the basin.

In some aspects, the exit 110 of the nozzle 103 is also designed toenable a spray cone to properly wet at least a portion of the packingmaterial 113 located below the basin and nozzle system 100, given thestatic head level at or above a liquid height 106 and the associatedliquid flow rate into the basin and nozzle system 100. In someembodiments, as the flow rate of fluid stream 101 increases to thebasin, the liquid and static head level in the basin will rise until itreaches level 107. In some embodiments, at and above this liquid andstatic head level 107, the next set of nozzles, 102 become active. Insome embodiments, these 102 nozzles could have a higher intake height,109, that prevents them from activating until a higher static head level107 is reached.

In some aspects, these 102 nozzles may also have enough liquid levelabove their intake height, shown as 108, to prevent syphoning of air. Insome embodiments, at least one of these nozzles, 103 and 102, can beplaced in certain patterns throughout the basin to accommodate how andwhere the stream 101 enters and fills the basin, to ensure that allnozzles are located to receive proper liquid flow and static head foroperation. In some aspects, once the range of liquid flow rates to thebasin are selected, the factors that must be considered to produceconsistent spatial liquid distribution may include the design of nozzles102 and 103, intake heights 105 and 109, the number of nozzles 102 and103, and the location and concentration of nozzles 102 and 103 withinthe basin. For example, the nozzles 103 and 102 may be paired besideeach other into a set, where the sets are distributed evenly within thebasin. In another example, the nozzles 102 may be located within thecentral portion of the basin and the nozzles 103 may be distributedevenly within the basin, but may also have a higher concentration ornumber of nozzles 103 located at the perimeter of the basin.

In another example, the nozzles 102 may be located within the portion ofthe basin furthest from the liquid inlet of the basin. Further to thisexample, if the liquid inlet was located on one wall of a square orrectangular basin, the nozzles 102 might be located in a single line forexample along the basin near the wall directly opposite to the wall onwhich the liquid inlet port was located. In all of these examples, thegeometry of nozzles 102 and 103 may be the same or different. In someembodiments, there can also be several different sets of these types ofnozzles 102 and 103, wherein the intake heights 105 and 109 are varied,as are the nozzle exit designs 104 and 110, to enable better wettingcapabilities under the stream 101 flow rates and basin static headlevels.

In some embodiments, the nozzles 102 and 103 may be of the same nozzledesign, for example they may be designed with a particular geometricexit shape, or inlet diameter, to provide a proper spray cone under lowflow conditions, however the number of nozzles attached to the higherintake height may be increased to correct for the higher flow case. Forexample, the basin could include 5 to 10 times more 102 nozzles attachedto higher intake heights than 102 nozzles attached to lower intakeheights, so that the combination of quantity and type of nozzles persquare foot of basin footprint allow for proper flow and spatial liquiddistribution to the packing at static head levels 106 or 107 andcorresponding liquid flow rates into the basin.

In some embodiments, the nozzles 102 and 103 may be of different nozzledesign, where the 102 nozzle design is specific to lower flow rates andthe 103 nozzle design is specific to higher flow rates, and thecombination of these nozzle designs and intake heights allow for properspatial liquid distribution under the various flow rates to the nozzleand basin system 100. In some embodiments, a combination of number andtype of nozzle designs attached to intake heights may provide properspatial distribution of liquid to the packing under various liquid flowrates.

Referring to FIG. 2A, a graph illustrating how the flow of stream 101could vary over time is shown, where a larger flush flow (Q_(flush))occurs, followed by no flow, followed by a smaller pulse flow(Q_(pulse)). In some embodiments, this method of flowing stream 101 tothe basin enables the packing material 113 to remain suitably wetted andcapable of capturing CO₂ while significantly reducing the pumping energyrequirements. The dashed red line, Q_(min), illustrates a minimum flowrate, above which the 102 type of nozzles become active.

Referring to FIG. 2B, a graph illustrating how the liquid flow throughthe packing material could vary over time in association with thevarious flow rates of stream 101 over time, where for example a largerflush flow (Q_(flush)) to the top basin occurs, followed by small or noflow, followed by a smaller pulse flow (Q_(pulse)), and this flowpattern may be repeated over time. In some aspects, this repeatingpattern of varying flow rates over time may be referred to as a dutycycle, as it can be produced by cycling an upstream pressurized liquiddistribution system that includes for example one or more pumps andvalves to control the flow. This upstream system requires energy tocycle through the various flow patterns, and the duty cycle is selectedto optimize this energy demand with CO₂ capture so that the overall aircontactor system is optimized for both operational and capital costs. Insome embodiments associated with these types of stream 101 flow patternsto the basin, the transition of liquid flow rates through the liquiddistribution system and top basin and/or the packing could become lesssharp as a result of the characteristic of the top basin and nozzledesign.

Referring to FIG. 3, a basin collection system for settling, collectionand removal of solids is described with respect to illustrative system300. The basin collection system 301 is fluidly coupled to packingmaterial 303, an inclined bottom basin area 305, a liquid redistributionpump 311 and associated suction intake and piping 310, and a solidscollection basin 309. The solids collection basin is fluidly coupled toa mechanical removal system 307. In some embodiments, liquid stream 302may include, for example, fluids such as water, NaOH, KOH or otherprocess solutions, and could also include suspended solids, for example,particulates captured by the liquid from the gas stream, or may includeparticulates entrained from upstream facilities. In some embodiments,stream 302 flows through packing material 303, is distributed and fallsoff the packing as small drops or trickles of liquid, 304, into theliquid collection basin system 301, where it comes into contact with aninclined bottom basin area 305. In some embodiments, some amount ofparticulates could be present in stream 302 and could settle out ontothe inclined bottom basin area 305, in particular when the flow rate ofliquid 304 across the inclined bottom basin area 305 towards the liquidredistribution pump's suction intake and piping 310 is low enough, theparticulate settling velocity is high enough, and the distance to theliquid redistribution pump's suction intake and piping 310 is far enoughto enable settling of the particulates out of the liquid flow before itreaches the redistribution pump's suction intake and piping 310.

In some embodiments, the basin bottom area 305 is inclined such that itremains largely above the liquid level 306 of the liquid collectionbasin system 301, and as a result, a solids layer 308 accumulates. Insome aspects, the motion of the liquid droplets 304 as they splash ontothe inclined bottom basin 305 surface is such that it displaces some ofthe solid layer 308 in a downward direction towards the solidscollection basin(s) 309. In some embodiments the solid collection basincould contain a mechanical removal system 307 for example an auger,screw conveyor, progressive cavity pump, screw pumps, high densitysolids pump such as reciprocating pumps, or the like, which removes thesolids material from the basin.

In some embodiments, the basin collection system 301 may be the sameshape and size as the footprint of the packing material 303, for examplerectangular if the packing footprint is rectangular or circular if thepacking footprint is circular, to ensure proper collection of theliquid. In some embodiments, at least one of the inclined bottom basin305 and solid collection basin(s) 309 allow for solids collection totake place in non-circular shapes of the footprint of the basincollection system 301.

In some types of commercial solids separation systems, for exampleclarifier settling tank designs, a circular footprint may be necessaryto gain full advantage of the use of solids removal equipment such assludge raking or suction systems, where a circular sweeping pattern canremove solids with fewer dead zones from a circular footprint than froma non-circular footprint.

FIG. 4 depicts an example precisely machined drift eliminator frameassembly system for minimizing air bypass with respect to illustrativesystem 400. The drift eliminator material 402 is coupled to apre-fabricated frame assembly 401 as part of a frame and drift assembly403, which is coupled to the air contactor structure walls 404. In someembodiments there may also be one or more fans, for example forced draft407 or induced draft 408 fans, coupled to the air contactor system 400.The drift eliminator material 402 is pre-installed into a pre-fabricatedframe assembly 401 such that the combined frame and drift assembly 403can be easily fitted over the air contactor structured walls, 404, andplaced next to the packing material 405, during, or after, install ofthe air contactor. In some embodiments, this framed drift eliminatorassembly 403 is precisely machined and fitted together in a controlledenvironment, such as a fabrication shop, where the precision and fittingcan be consistently executed and checked for quality, in some casesthrough use of an automated assembly line, before being installed on theair contactor system. In some aspects, this method of pre-fabrication ofthe drift eliminator assembly can lead to substantially no air gaps, andcracks between the drift eliminator material and other componentry than,for example, if all componentry was installed individually in the field.In some embodiments, this framed drift eliminator assembly 403 ispre-fabricated in a controlled, consistent and precise manner such thatthe airflow, 406, cannot bypass the drift eliminator material 402 byslipping through gaps or cracks. In some aspects, pre-fabricating theframed drift eliminator assembly in a controlled, consistent and precisemanner means that the drift eliminator assembly is built and sealed inthe essentially the same way, using essentially the same methods, undersimilar conditions, and inspected to the same level of quality for allapplications such that each framed drift eliminator assembly conforms toa standard. This is different from, for example, installing and sealingthe drift eliminator material in the field under various environmentalconditions, for example freezing temperatures, snow, wind or rain, insome cases using various labour, equipment, install and inspectionmethods with a higher degree of variation in the formation of drifteliminator material around support structures, and a higher degree ofvariation in the quality of inspection, resulting in a higher degree ofgaps or cracks produced, leading to the increased potential of airbypass. The air flow may be moved by a forced fan configuration, 407,where the fan is located upwind of the packing material, 405, or it maybe pulled by an induced fan configuration, 408, where the fan is locateddownwind of the packing and drift material. In any case, the drifteliminator assembly/install/sealing embodiments disclosed here ensuresthat the bulk air leaving the system is ultra-low in drift content(there are substantially no air gaps) and process solution does notbecome air borne outside of the system.

FIG. 5 depicts an example of precisely fitted flexible seals forminimizing air bypass with respect to illustrative system 400. The drifteliminator material 402 is coupled to a pre-fabricated frame assembly401, which is also coupled to flexible seals 500 as part of a frame anddrift assembly 403, which is coupled to the air contactor structurewalls 404. In some embodiments there may also be one or more fans, forexample forced draft 407 or induced draft 408 fans, coupled to the aircontactor system 400. The flexible seal material 500 is attached to theframed drift eliminator assembly 403 to further reduce air bypass,resulting in substantially no air gaps, around the drift eliminatormaterial 402.

Referring to FIGS. 6 and 7 (showing elevation and plan views,respectively), installing and sealing the drift eliminator material isdescribed with respect to illustrative gas contactor system 600. Thesystem described herein may include an induced fan 607 coupled to drifteliminator material 602 and structural housing 604 as well as sealant603. The structural housing may be coupled to one or more areas ofpacking material 605, an open plenum area 601 and a fan cowling outlet608. The system described is shown as an induced flow dual cell crossflow gas contactor. In this configuration, the fan 607 is locateddownwind of the packing and drift material, and it functions to pullairflow 606 into the system, through the packing material 605 andthrough the drift eliminator material 602 before leaving via the fancowling outlet 608. In some applications, the system could also be aninduced flow single cell gas contactor. The drift eliminator material602 is installed immediately below the fan cowling 608 and the edges ofthe drift eliminator material are sealed against the structure/housing604. The sealant 603 may be constructed of a flexible and air tightmaterial, and will be chemically compatible and inert in regards to theprocess solution. The sealant may include but is not limited tomaterials such as flexible flaps or strips, caulking or spray foam, andmay be constructed from material that is compatible with causticsolutions including but not limited to potassium or sodium hydroxide.This configuration ensures substantially no air gaps or cracks, so thatall gas/liquid flow in the open plenum area 601 cannot be sucked out ofthe system by the fan without passing through the drift eliminatormaterial. Induced fan configurations are also desirable, as while theyare operating, they create a pressure gradient where the outsidepressure is greater than the system pressure, so that gas leaks into thesystem rather than out of the system.

Referring to FIGS. 8 and 9 (showing elevation and plan views,respectively), installing and sealing drift eliminator material isdescribed with respect to illustrative gas contactor system 600. Thesystem described herein may include a fan cowling 608 coupled to aninduced fan 607 and a structural housing 604. The structural housing 604may be coupled to one or more sections of packing material 605, drifteliminator material 602 and sealant 800. The structural housing 604 mayalso be coupled to an open plenum area 601. The system described isshown as an induced flow dual cell cross flow gas contactor. In thisconfiguration, the fan 607 is located downwind of the packing and driftmaterial, and it functions to pull airflow 606 into the system, throughthe packing material 605 and through the drift eliminator material 602before leaving via the fan cowling outlet 608. In some applications, thesystem could also be an induced flow single cell gas contactor. Thedrift eliminator material, 602, is installed immediately downwind of thepacking material, 605, and in some cases could be physically attached tothe packing material. The edges of the drift eliminator material 602 aresealed against the structure/housing 604 using a sealant, 800 such thatthere are substantially no air gaps or cracks. The sealant, 800, may beconstructed of a flexible and air tight material, and will be chemicallycompatible and inert in regards to the process solution. Induced fanconfigurations such as this one are also desirable, as while they areoperating, they create a pressure gradient where the outside pressure isgreater than the system pressure, so that gas leaks into the systemrather than out of the system.

In the embodiments described above and illustrated in FIGS. 4 through 9,the notion of substantially no air gaps or cracks can mean that between0-1% of the total outlet surface area is not directly covered by drifteliminator material. The outlet surface area is the area through whichthe gas being drawn through the liquid-gas contactors must move in orderto exit the system, and may be located downstream of the packingmaterial. As shown in FIGS. 4 through 9, the outlet surface area mayinclude but is not limited to the area immediately adjacent to thepacking material 605, the surface area immediately upstream of the fan607 and cowling 608, and the area downstream of the packing 605 butupstream of the plenum 601.

Referring to FIG. 10, a carbon dioxide capture facility 10 isillustrated comprising packing 12 formed as a slab 15, the slab 15having opposed dominant faces 14, the opposed dominant faces 14 being atleast partially wind penetrable to allow wind to flow through thepacking 12. At least one liquid source 16 is oriented to direct carbondioxide absorbent liquid into the packing 12 to flow through the slab15. The slab 15 is disposed in a wind flow 18 that has a non-zeroincident angle with one of the opposed dominant faces 14. The packing 12may be oriented to direct the flow of carbon dioxide absorbent liquidthrough the slab 15 in a mean flow direction 20 that is parallel to aplane 22 defined by the opposed dominant faces 14. It should beunderstood that opposed dominant faces 14 don't have to be exactlyparallel.

In one embodiment, the faces 14 may be converging, diverging, or curvedfor example. Packing 12 may be oriented to allow the carbon dioxideliquid absorbent to flow through the packing 12 by gravity. In someembodiments, packing dimensions can be about 200 m× about 20 m by about3 m contained in a structure measuring about 25 m×7 m. In someembodiments, dimensions can range from about 10 m× about 7 m× about 2 mto about 1000 m× about 50 m× about 15 m.

Referring to FIG. 10, the non-zero incident angle refers to the factthat wind flow 18 strikes the face 14 at an angle greater than zero.This may be contrasted with traditional packing arrangements, where gasis flowed through a tower of packing starting from the very bottom. Insome embodiments, the non-zero incident angle is orthogonal with the oneof the opposed dominant faces. It should be understood that the non-zeroincident angle may be within 10% of exactly orthogonal. The non-zeroincident angle may also refer to the mean angle of flow of the wind. Themean angle of flow of the wind may be averaged over a period of time.

Referring to FIG. 10, the opposed dominant faces 14 may be orientedvertical. The orientation of faces 14 may be determined relative to, forexample, the ground. In other embodiments, faces 14 may be oriented atan angle to the ground, e.g., slanted.

In another embodiment, the opposed dominant faces 14 may be orientedhorizontal (not shown). This embodiment tends to have a larger footprintthan the vertical slab embodiment.

Referring to FIG. 10, the at least one liquid source 16 may furthercomprise at least one pump 26. Pump 26 may have several distributionpipes 28, controlled by a valve (not shown), in order to selectivelyapply liquid into various sections of packing 12. In some aspects, thedistribution pipes 28 may apply liquid into various top basin andnozzles systems instead of directly to the various sections of packing.The at least one pump 26 may be configured to supply the carbon dioxideabsorbent liquid in a series and combinations of flush flows, low or noflows, and pulses. In some embodiments, the use of pump 26 and severaldistribution pipes 28 to apply liquid into various sections of packingis done to ensure that the same duty cycle is applied to any or allgiven sections or packing within the air contactor system.

Referring to FIG. 10, at least one fan 30 may be oriented to influencewind flow through at least a section of one of the opposed dominantfaces 14 of the packing 12. Fan 30 may be reversible. In someembodiments, fan 30 may prevent the wind flow that has already flowedthrough the packing 12 from circulating back into the packing 12.

Referring to FIG. 10, the at least one fan 30 may further compriseplural fans, each of the plural fans being oriented to influence windflow through at least a respective portion of the packing 12. In someembodiments, the respective portion is understood as being the portionof the packing 12 that air flow through fan 30 would have the greatestinfluence over, for example the packing 12 most adjacent or closest tofan 30. The at least one fan 30 may be provided as part of a fan wall 32adjacent at least one of the opposed dominant faces 14. It should beunderstood that fan walls (not shown) may be located adjacent each offaces 14. Adjacent, in this document, is understood to mean next to, andcan include embodiments where the fan wall 32 is spaced from, butadjacent to, face 14. Referring to FIG. 10, the fan wall 32 may beadjacent the one of the opposed dominant faces 14 through which the windflow 18 is exiting the packing 12. In fan wall 32, the individual fansmay be separated by impermeable material. The fans 30 create a pressuredrop across the wall 32, which drives flow through the packing 12. Insome embodiments, fan wall 32 is designed such that, in the event that afan fails, and ultimately blocks of its respective flow, flow throughthe packing 12 would be almost, if not completely, unaffected. This maybe accomplished by closely spacing adjacent fans, and by spacing the fanwall 32 from the packing 12, for example.

Referring to FIG. 10, a sink 46 may be provided for collecting carbondioxide absorbent liquid that has flowed through the packing 12. In someaspects, the sink 46 may be, for example a concrete-lined basin thatcatches the hydroxide and contains supports to hold the packing. In someembodiments, there may be a gap between the packing 12 and the sink 46that can be −1 to 1.5 m for example. In some embodiments (not shown),sink 46 may be a pipe or a series of conduits for example, thattransport the liquid directly from packing 12. This type of system mayinvolve a funneling or drainage apparatus designed to focus the drainageof the liquid into a single, or a network of pipes. The contacted liquidmay then be recirculated through the packing, or it may be recycled andthen recirculated. In some embodiments, facility 10 further comprises arecycling system (not shown) for regenerating spent carbon dioxideabsorbent liquid. The recycling system may be, for example, any of thesystems for recycling spent carbon dioxide liquid absorbent. The carbondioxide absorbent liquid may comprise a hydroxide solution, for examplea sodium hydroxide solution. The source of liquid 16 preferably suppliesrecycled carbon dioxide absorbent liquid.

Referring to FIG. 10, the step of applying may further comprise applyingthe carbon dioxide absorbing liquid into at least one of a topdistribution nozzle and basin system (not shown) and/or a first portionof packing 12 in a first series of flow rates, for example flushesand/or pulses, and applying the carbon dioxide absorbing liquid intoanother top distribution nozzle and basin system and/or a second portionof packing 12 in a second series of flow rates, for example flushesand/or pulses. This may be envisioned by selectively applying liquid viadistribution tubes 28A and 28B to at least one of a top distributionnozzle and basin system and/or a portion of packing 12. Because tubes28A and 28B only feed a portion (e.g., the left-most portion) of atleast one of a top distribution nozzle and basin system and/or packing12, only that nozzle and basin system and/or portion or packing willhave liquid applied to it. Liquid may then be selectively applied to theright hand of at least one of a top distribution basin system and/orportion packing 12 by applying liquid via tubes 28C and 28D. The firstand second series of flow rates may be synchronized, asynchronized,completely different, or synchronized out of phase with one another, forexample, allowing fluids to be supplied intermittently from acontinuously operating pump and valve system.

Referring to FIG. 10, the packing may be oriented to flow the carbondioxide absorbing liquid through the packing 12 in a mean liquid flowdirection 20. Flowing may further comprise flowing the gas through thepacking 12 obliquely or perpendicularly to the mean liquid flowdirection 20. This is advantageous as the flow of gas may have adifferent flow direction than, and one that is not counter current to,the mean liquid flow direction 20 of the liquid. Thus, a larger surfacearea of the packing may be used to full advantage, greatly increasingthe quantity of wind or gas that may contact liquid in packing 12 over acourse of time while still allowing the liquid to pass through and drainfrom packing 12.

In these embodiments, a slab is not entirely necessary, in fact othershapes of packing 12 are envisioned, including but not limited to acube, a cylindrical, and other various shapes. Referring to FIG. 10, insome embodiments flowing the gas further comprises flowing the gasthrough the packing 12 perpendicularly to the mean liquid flow direction20. It should be understood that exact perpendicularity is not arequirement. Flowing may further comprise flowing the gas through atleast one of the opposed dominant faces 14, for example through both offaces 14 as indicated.

As disclosed above, these methods may involve recycling the carbondioxide absorbing liquid. The methods may involve influencing theflowing of the gas through the packing. Influencing may comprise, forexample, preventing the gas that has already flowed through the packing12 from circulating back into the packing 12. Influencing may furthercomprise driving the flowing of the gas in a drive direction that is atleast partially oriented with an ambient wind flow direction. This maybe carried out using fans 30, which may be reversible in order to carryout this function. Further, these methods may involve directing the flowof gas at least one of into and out of the packing, using, for examplelouvers.

Referring to FIG. 10, in some embodiments, fans 30 may be reversible inorder to enable the flow to be driven in the direction of the ambientwind field, which is more efficient than inducing a flow that is counterto the prevailing wind direction. In some aspects, the orientation ofslabs 15 may be such that prevailing wind 18 is perpendicular to theslab 15, and is in the direction at which the fan wall (not shown) worksmost efficiently. The packing design may use vertically oriented plates.This would be a modification of conventional structured packing designedto enable, for example, orthogonal liquid and gas flow directions.Packing may be for intermittent fluid flow so as to maximize the hold upof liquid absorbent inside the packing material.

Referring to FIG. 10, as disclosed above, the fan wall 32 may besectionalized, so that flow speed can be reduced or stopped when fluidis flowing to minimize fluid loss. The sections may be operatedasynchronously so that only one section at a time is receiving the fluidflow enabling fluid pumps to operate continuously. For example, if fluidflow was needed for 100 seconds out of 1000 one may have 11 sections andwould direct the fluid into one of them at a time.

Referring to FIG. 10, another method of carbon dioxide capture isillustrated. Carbon dioxide absorbing liquid is flowed through packing12 in a mean liquid flow direction 20, a gas containing carbon dioxideis flowed through the packing 12 obliquely or perpendicularly to themean liquid flow direction 20 to at least partially absorb the carbondioxide from the gas into the carbon dioxide absorbing liquid. Flowingcarbon dioxide absorbing liquid through packing 12 may further compriseapplying the carbon dioxide absorbing liquid into the packing 12 in aseries of pulses. Flowing the gas further may comprise flowing the gasthrough the packing 12 perpendicularly to the mean liquid flow direction20.

A method of contacting a liquid with a gas is also disclosed comprisingapplying the liquid into packing 12 in a series of pulses and flowingthe gas through the packing 12.

Referring to FIG. 10, a gas-liquid contactor (illustrated by facility10) is also disclosed. Referring to FIG. 10, the contactor (illustratedas facility 10) comprises packing 12 formed as a slab 15, the slab 15having opposed dominant faces 14, the opposed dominant faces 14 being atleast partially wind penetrable to allow wind to flow through thepacking 12. At least one liquid source 16 is oriented to direct theliquid into the packing 12 to flow through the slab 15. The slab isdisposed in a wind flow 18 that has a non-zero incident angle with oneof the opposed dominant faces 14. Similar to the gas-liquid contactorand the above described method, this method may be applied to anygas-liquid contactor. It should be understood that this gas-liquidcontactor may have all of the same characteristics as the carbon dioxidecapture facility and contactor disclosed herein.

Referring to FIG. 10, a gas-liquid contactor (illustrated by facility10) is also disclosed, comprising a slab 15 structure comprising packing12 and a liquid source 16 oriented to direct the liquid into the packing12 to flow in a mean liquid flow direction 20. The slab structure isdisposed in a wind flow 18 that flows obliquely or perpendicularly tothe mean liquid flow direction 20.

Referring to FIG. 10, a method of contacting a liquid with a moving gas(illustrated as wind flow 18) is disclosed. The method comprises flowingthe liquid through packing 12, and driving the moving gas through thepacking 12 in a drive direction (which is the same as wind direction 18in this embodiment) that is at least partially oriented with an ambientflow direction 18 of the moving gas. In the embodiment shown, theflowing gas is wind, and the ambient flow direction is the ambient winddirection 18. This method may further comprise reversing the drivedirection when the ambient flow direction 18 reverses. Reversing the fandirection (or more generally, reversing the forced flow of air throughthe packing) in such a way as to drive the air with a vector directionthat is at least partially oriented with the ambient wind 18 reduces therequired fan power. Further, this reduces the amount of low-C02 air thatis recycled back into the inlet of the system, thus improving itsefficiency. It is thus advantageous to align the packing such that oneof opposed dominant face 14 is roughly perpendicular to the prevailingwind, in order to maximize the efficiency of the fans. In this document,wind flow is understood as moving gas containing CO₂.

Referring to FIG. 11, an air contactor system 1500 including one or moreof the features described in FIGS. 1 through 10, is described withrespect to illustrative a Direct Air Capture process 1200. In someembodiments, a Direct Air Capture process includes but is not limited toa causticization system 1025, a calcining system (not shown), a slakingsystem (not shown) and an air contactor system 1500. FIG. 11 does notshow all the systems and equipment involved in a direct air captureprocess, rather, it illustrates one embodiment of how the keyinterfaces, for example heat and material stream exchanges, could be setup between an air contactor system 1500 and the immediate upstream anddownstream process and heat exchange equipment of a direct air captureprocess. In some aspects the direct air capture process may include acontrol system 999 coupled to the components (illustrated or otherwise).

In some embodiments, the capture solution may be composed of potassiumhydroxide and potassium carbonate in water. In some aspects, thesolution circulates internal to the air contactors to keep a wetted filmreplenished on fill media known as structured packing. As this solutionreacts with carbon dioxide, the hydroxide is depleted as carbonate isproduced. To keep the solution composition at desired concentration, acarbonate-rich bleed stream can be removed from the air contactor lowerbasin and sent downstream, for example to a causticization systemincluding but not limited to equipment such as a fluidized bed reactivecrystallizer, (also known as a pellet reactor), while a carbonate-lean,hydroxide-rich return stream carries solution from the downstreamcausticization system back to the air contactor system.

Referring to FIG. 11, stream 900 represents inlet atmospheric airflowinto the air contactor. Stream 901 represents outlet carbondioxide-depleted air. Stream 904 represents the potassium hydroxideaqueous solution delivered to the packing structure of the aircontactor. In some aspects, the potassium hydroxide aqueous solution isdelivered through use of a top basin and nozzle system as described inFIG. 1. In other aspects, the liquid may be distributed using adistribution header system, including pressurized piping and nozzles.

In some embodiments, stream 904 is a pulsed flow, cycling the flow ofcaustic solution intermittently to the top of the air contactor insteadof supplying it continuously. In some aspects, wetting of the packing ismaintained at low average flow rates by alternating short-periods ofhigh-flow rates that wet the packing and remove dust and debris, and lowflow rates that replenish the wetted surface.

In some embodiments, stream 911 could be re-circulated potassiumhydroxide solution that is fed back to the air contactor system 1500,for example to the basin 1005, or to the top of the packing structure1000 via stream 914, after processing in the downstream causticizationsystem 1025, which could include for example a causticizer or pelletreactor. The re-circulated solution stream 911 may include a smallquantity of calcium carbonate fines from the causticization system 1025,which may be filtered out of the stream 910 using for example at leastone of an inline fines filter (not shown) fluidly coupled to stream 910.In another aspect, these solids may settle out in the basin 1005 of theair contactor system, where for example the basin 1005 could includesolids removal features including but not limited to those described inFIG. 3. The solution from stream 910 may temporarily be stored a tank1035 before being transferred by pump 1040 as stream 911 to aircontactor system 1500.

In some embodiments, carbon dioxide-rich solution is extracted from theair contactor basin 1005 through a pump 1010 as stream 902. A portion ofthis hydroxide-based stream 904 is re-circulated to continue carbondioxide capture in the air contactor unit 1005.

In some embodiments, during the process of capturing carbon dioxide, theair contactor 1000 may also evaporate water to the atmosphere, causingevaporative cooling which reduces the temperature of the rich solutionstream 902 leaving the contactor. This cooled solution 903 may then besent to a heat exchanger 1010 where it cools streams of water 905, 906that can be used to cool other plant equipment as required.

In some embodiments, after the rich solution 907 has passed through theheat exchanger 1020 and is warmed back to approximately 20° C., a smallstream (not shown) may be drawn off for disposal to manage the build-upof non-process elements ingested by the contactor.

These non-process elements may include for example, dust, pollen, otherparticulates, and ions produced by the reaction of the hydroxide withother acid gases present in the air.

The flow rate of hydroxide-based stream 904 is set by the needs of thepacking material in the air contactor 1000 to ensure an optimum amountof wetted surface area for capturing the carbon dioxide from theincoming air. The optimum point is determined by a balance of what isrequired for the reaction kinetics as well as what is required to wetthe packing surface.

In some embodiments, the causticization system 1025 receives the carbondioxide-rich solution stream 907, which may contain for example aqueouspotassium hydroxide and potassium carbonate, from the air contactor unit1000. In some aspects, the causticization system 1025 receives acontrolled amount of concentrated calcium hydroxide slurry (hydratedlime slurry) by way of stream 908 from a slaker system (not shown).These two streams 907 and 908 feed into the causticization system 1025.In some cases, where the causticization system 1025 includes for examplea fluidized bed reactive crystallizer, the two streams 907 and 908 maycombine with a recirculation stream 909 before re-entering thecausticization system 1025. The causticization reaction takes place inthe causticization system, reacting calcium and hydroxide ions withpotassium and carbonate ions to produce aqueous potassium hydroxide andsolid calcium carbonate.

In some embodiments, the effluent fluid containing fines leaves thecausticization system 1025 as stream 910, and discharges back to the aircontactor system as stream 911. In some aspects, the causticizationsystem 1025 may include for example a pellet reactor unit, and thepellet reactor unit may have a recirculation stream 912 which leavesfrom the top portion of the pellet reactor and is then pumped back intothe pellet reactor as stream 909 by way of pump 1030. In some aspectsthe recirculation stream 912 provides at least a portion of thefluidization flow needed to fluidize the pellet bed.

In some aspects of a DAC facility 1200, for example where thecausticization system includes a pellet reactor, a mixture of mostlymature pellets from the pellet reactor unit may be discharged as aslurry of pellets in stream 913, and sent to a separation unit (notshown) and a washing unit (not shown).

In some embodiments, the air contactor design may include for example a“structured packing” material that distributes the carbondioxide-absorbing solution over a large surface area, and createsefficient contact with the air by minimizing frictional air resistance(pressure drop), in the flow channels. In some aspects, the large liquidsurface area is essential in order to absorb a large fraction of carbondioxide from the air, and the low-pressure drop is required to minimizethe fan energy requirements at high air throughputs.

In some aspects, the term “structured packing” may include a bulk fillmaterial. In some aspects the term “structured packing” may includematerial that is composed for example of crimped or pressed sheets, andmade for example from steel or plastic componentry that may be assembledto form a multitude of gas flow channels. In some aspects, thestructured packing is designed to disperse liquid that is supplied fromoverhead through use of distribution componentry. In some aspects, thedistribution componentry may include a basin and nozzle system, or adistribution of pipes, valves and nozzles

In some embodiments, the air contactor system may include PVC-basedpacking products from the cooling tower industry, which could beselected based on, for example, cost-effectiveness, chemicalcompatibility with hydroxide, high surface area, long lifetime, debrismanagement, and low pressure drop.

In some embodiments, using PVC instead of stainless steel material inthe air contactor design could offer dramatic cost savings for alarge-scale air contactor. Moreover, in some aspects, plastic packingoffers wetting comparable to steel packing for strong hydroxide, and theperformance of plastic cooling tower packing typically exceeds that ofsteel cooling tower packing in pressure drop per unit of surface area.

In some embodiments, cooling tower packing material similar to BrentwoodIndustries XF12560 structured packing, a commercially available productspecifically designed for use in large cross-flow cooling towerapplications, may be used in the air contactor design. Brentwood XF12560is constructed from PVC that is completely resistant to stronghydroxide, has an efficient cross-flow geometry which produces lowair-side pressure drop, and possesses a similar surface area per volume(210 m²/m³) as common stainless steel tower packing, such as Sulzer250X.

In some embodiments, replenishment of the capture solution that forms afilm on the walls of the air flow channels within the packing of the aircontactor system is accomplished simply by pumping liquid to the top ofthe air contactor and distributing it over top of the packing banks. Insome aspects, this could involve the use of distribution pipes andnozzles. In some aspects this could involve variations of the top basinand nozzle design described herein and illustrated in FIG. 1. In someaspects, simple arrangements of pipes, pumps, and control valves, allowthe liquid flow to be controlled to the top of the air contactor, and toany variation of distribution system that is fluidly coupled to the topof the air contactor.

In some embodiments, minimizing the energy required to operate thegas-liquid contactor can be a critical factor in the design. In someaspects where the air contactor is used to capture CO₂, for example fromdilute sources such as atmosphere, the design of the air contactorsystem can involve a trade-off between generating sufficient airthroughput for carbon dioxide capture, and minimizing capital andoperating costs to maintain the economic viability and environmentalsustainability of the process. Air contactor designs for applicationssuch as carbon capture from dilute sources can be a product of balancingthe operating costs of fan and liquid pumping energy requirements togenerate sufficient air throughput and carbon dioxide capture—whileminimizing the capital expenditure per unit of carbon dioxide capturedand overall carbon intensity of the process itself.

In some embodiments where the gas contactor is used to capture CO₂ fromdilute sources such as atmosphere, the air contactor design can requirebetween approximately 4 to 9 meters of air travel depth for optimumperformance. The air travel depth refers to the linear distance ofpacking material through which the air flows and interfaces with theliquid solution. In comparison to short air travel/packing depths of upto approximately 1 meter, for example those used in cooling towerapplications, longer air travel depths may produce larger pressure dropsfor a given liquid flow, air velocity and packing material. The largerpressure drop can result in the need for more powerful fan designs andhigher energy use, in particular if continuous high liquid flow rateswere to be used to meet the vendor wetting requirements of the packingmaterial.

Given the nature of carbon capture applications, e.g., the mainobjective being to reduce carbon intensity with an economically viableprocess/design, there is strong incentive to find ways to minimizeenergy usage, while maintaining attractive capital expenditure per unitof carbon dioxide captured and low overall carbon intensity.

In some embodiments, the use of variable liquid flow in a gas-liquidcontactor allows for energy savings in both the air fan and liquid pumpoperations. For example, liquid can be supplied to the packing materialin periods of high liquid-flow rates to fully flush the entire packingsurface, and subsequent periods of low or zero flow rates to conservepumping energy while allowing the hydroxide solution to partly reactaway while capturing carbon dioxide. This method of operation canminimize the pressure drop of the packing material by avoidingair-channel constriction with high liquid flows, while also minimizingpumping energy requirements.

One way of supporting a variable flow rate mode of operation is throughuse of the nozzle and basin features described herein. The nozzle basinfeature allows for consistent liquid spatial distribution throughout therange of flow rates so that the packing material is evenly wetted,resulting in a greater portion of the packing material participating inthe CO₂ capture process throughout the range of liquid flow rates.

The economic benefits of reducing overall energy requirements asdescribed above may be applied to other gas contacting systems, and assuch the use of variable flow rates and the nozzle basin featuresdescribed here could be useful in other applications, for examplecooling tower applications as well as carbon capture from point sources.

In some embodiments, the air contactor system is used to capture carbondioxide directly from air, where it exists at the low concentration ofapproximately 400 ppm. The bulk air processing requirements for thisimply that traditional packed scrubber column technology is poorlysuited to the task. Rather, designs that are more similar to, forexample, industrial cross-flow cooling towers, having morecost-effective structural designs and larger inlet areas, could providea more appropriate design basis.

In some embodiments, the use of air contactor designs that resemblelarge, cross-flow cooling tower structures instead of a packed towerconfiguration allows for significantly lower cost per enclosed packingvolume.

In some embodiments, by applying construction materials andmethodologies similar to those applied in the cooling tower industry tothe air contactor design, a reduction in the structure cost per inletarea could be realized.

In some embodiments, the air contactor structure itself has inlet areadimensions determined by the required capture rate of carbon dioxide andthe density of carbon dioxide in air, and has depth determined withinthe overall optimization. In some aspects, the air contactor structureitself could utilize a combination of fibreglass reinforced plastic andsteel materials to create the support structure. In some embodiments,particularly larger scale applications, liquid distribution systems arecontained within the support structure, packing banks are supported overliquid collection basins, and air flow is managed with cowlings andbaffles.

In some larger commercial plants, the air contactor system could includefor example multiple air contactor modules fluidly coupled to eachother.

In some embodiments, the air contactor support structures could befabricated and constructed using common cooling tower components andmethods, in addition to the features described in FIGS. 1 through 10.

In some embodiments, the packed air travel depth, the horizontaldistance between the inlet and outlet of the structured packing throughwhich the air travels, and optimal air velocity for the air contactor,may be determined based on a trade-off between capital and operatingexpenses. In some aspects, the air contactor design is a product ofbalancing the operating costs of the fan(s) and liquid pumping energyrequirements to generate sufficient air throughput—and thus carbondioxide capture—while minimizing the capital expenditure per unit ofcarbon dioxide captured.

Operation of the air contactor design should take into account theprincipal environmental health and safety risks. Some examples of healthand safety risks could include for example, loss of corrosive hydroxidesolution through liquid spills, and through inclusion in the outlet airstream, known as drift. Liquid spills can be mitigated with standardcontainment designs and adherence to occupational health, safety, andenvironmental regulations. Drift is a term used in the cooling towerfield to denote fine aerosol particles that are generated by liquidmovement within the system. The loss of hydroxide through drift can be arisk associated with air contactor operation.

The cooling tower field has a well-developed method for driftelimination: commercial drift eliminators. Drift eliminators also knownas demisters, are very similar to structured packing: they force the airthrough a tortuous flow path, such that in making multiple bends, anyfine droplets entrained in the flow are strained out by the walls anddrain back into the system.

There are various types of drift eliminators commercially available.Drift eliminators can be integrated with the packing material of the aircontactor design. For example, a Brentwood Industries XF80Max stockdemister product, assures drift losses below 0.0005% of the full fluidrecirculation rate, even under high liquid flow conditions used incooling towers. At this performance level, commercially available drifteliminators are able to control drift in the air that passes throughthem at levels far below the regulated health and safety standards. Insome aspects, for example in cooling tower system installations wherecomponents such as drift eliminators may be installed and sealed in thefield, air bypass of the drift eliminator material can arise as a resultof, for example, the field installation methods or environmentintroducing cracks or gaps around the drift eliminator material. Forexample the drift eliminator material might be cut to fit aroundstructural beams or componentry, or installation or sealing activitiescould take place in the field, outdoors, in inclement weather and bydifferent installation teams. In some cases, these conditions mayincrease the likelihood of cracks or gaps formed between the packing,drift eliminator material and external structure, leading to some of theair containing liquid droplets (drift) moving around instead of throughthe drift eliminator material.

In some embodiments, the environmental, health and safety risksassociated with hydroxide solution drift can be effectively managed withproper drift eliminator installation. In some aspects, the examples ofdrift eliminator design, fabrication and installation as describedherein, and as shown in FIGS. 4 through 9, can enable lower drift levelsfor the overall air contactor system as these features work to preventair from bypassing the drift eliminator material.

In some embodiments, operation of the air contactor design, requirestight control of the aerosol droplet losses, or drift, tighter than thecontrol established for cooling tower designs, because the driftincludes more than just water. For example, the drift may containdroplets of hydroxide solution, which would pose environmental, health,and safety risks that are different to and potentially more severe thandrift of cooling water droplets. The 0.0005% performance rating ofexisting cooling tower drift eliminators suggests that they should beable to limit hydroxide drift losses to less than one-tenth of the NIOSHRecommended Exposure Limit, provided that they are designed, fabricatedand properly installed to mitigate the risk of air or liquid bypassingthe drift eliminator material.

In some embodiments, the air contactor unit may be fabricated usingin-shop modular construction, where modules are fabricated pre-assembledand tested at the fabrication location before being shipped to thefield. In some embodiments, air contactor componentry such as structuralhousing, packing, drift eliminators, that are designed for this type ofmodular fabrication will have overall cost savings, as there will be thepotential to reduce field install activities and site labour.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims. Further modifications and alternative embodiments of variousaspects will be apparent to those skilled in the art in view of thisdescription. Accordingly, this description is to be construed asillustrative only. It is to be understood that the forms shown anddescribed herein are to be taken as examples of embodiments. Elementsand materials may be substituted for those illustrated and describedherein, parts and processes may be reversed, and certain features may beutilized independently, all as would be apparent to one skilled in theart after having the benefit of this description. Changes may be made inthe elements described herein without departing from the spirit andscope as described in the following claims.

What is claimed is:
 1. A method of drift elimination in a liquid-gascontactor system comprising: configuring a pre-fabricated mechanicalframe coupled to a drift eliminator material to produce a framed drifteliminator assembly with substantially no air gaps between the drifteliminator material and the pre-fabricated mechanical frame; andcoupling the framed drift eliminator assembly to the liquid-gascontactor system.
 2. The method of claim 1, wherein the framed drifteliminator assembly comprises a flexible sealant coupled to the drifteliminator material.
 3. The method of claim 1, further comprisingcapturing CO₂ from at least one of a dilute source or a point sourcewith the liquid-gas contactor system.
 4. The method of claim 3, whereinthe dilute source comprises air and the point source comprises one ormore of flue gas, reservoir gas, exhaust flue stack gases from powergeneration processes, exhaust flue stack gases from concrete productionprocesses, or exhaust from combustion processes.
 5. The method of claim1, further comprising operating the liquid-gas contactor system as partof a cooling water system.
 6. The method of claim 2, further comprising:capturing CO₂ from at least one of a dilute source or a point sourcewith the liquid-gas contactor system, where the dilute source comprisesair and the point source comprises one or more of flue gas, reservoirgas, exhaust flue stack gases from power generation processes, exhaustflue stack gases from concrete production processes, or exhaust fromcombustion processes; and operating the liquid-gas contactor system aspart of a cooling water system.
 7. A liquid-gas contactor apparatuscomprising: a drift eliminator assembly comprising: a pre-fabricatedmechanical frame; a drift eliminator material coupled to thepre-fabricated mechanical frame to form a framed drift eliminatorassembly; and a flexible sealant pressed against the drift eliminatormaterial configured for substantially no air gaps; a packing material;and a fan positioned to circulate a gas stream through the packingmaterial.
 8. The apparatus of claim 7, wherein the liquid-gas contactorapparatus is configured for capturing CO₂ from one or more of a dilutesource or a point source.
 9. The apparatus of claim 8, wherein thedilute source comprises air and the point source comprises one or moreof flue gas, reservoir gas, exhaust flue stack gases from powerproduction equipment, exhaust flue stack gases from concrete productionequipment, or exhaust from combustion equipment.
 10. The apparatus ofclaim 7, wherein the liquid-gas contactor apparatus is configured aspart of a cooling water system.
 11. A liquid-gas contacting system, thesystem comprising: a packing material; a drift eliminator material; afan positioned to circulate a gas stream through the packing materialand the drift eliminator material; a liquid flowable through the packingmaterial and configured to capture carbon dioxide (CO₂) from at leastone of a dilute source or a point source; and a sealant positionedbetween the drift eliminator material and a housing, the sealantconfigured to minimize bypass of the gas stream between the drifteliminator material and the housing.
 12. The liquid-gas contactingsystem of claim 11, wherein: the drift eliminator material is positionedbetween the packing material and the fan; and the fan comprises aninduction fan.
 13. The liquid-gas contacting system of claim 11 whereinthe sealant comprises at least one of flexible flaps, flexible strips,caulking foam, and spray foam.
 14. The liquid-gas contacting system ofclaim 11 further comprising: a liquid inlet port coupled to a nozzle andbasin system; and a distribution sub-assembly coupled to the nozzle andbasin system configured to operate under a plurality of liquid flowrates while maintaining consistent spatial liquid distribution, thedistribution sub-assembly comprising: a first portion of nozzles havinga first intake height and a first nozzle design specific to a first flowrate; and a second portion of nozzles having a second intake heightshorter than the first intake height and a second nozzle design specificto a second flow rate that is less than the first flow rate.
 15. Theliquid-gas contacting system of claim 11 wherein the fan comprises a fancowling, and the drift eliminator material is coupled to the fancowling.
 16. The liquid-gas contacting system of claim 15, wherein thepacking material comprises a first section of packing material, thesystem further comprising a second section of packing material, and thedrift eliminator material is positioned between the first and secondsections of packing material and the fan.
 17. The liquid-gas contactingsystem of claim 16, wherein the first section of packing material, thesecond section of packing material, the drift eliminator material, andthe fan are configured to form a dual cell induced flow contactor. 18.The liquid-gas contacting system of claim 11 wherein the drifteliminator material is attached to the packing material.
 19. Theliquid-gas contacting system of claim 18, wherein the packing materialcomprises a first section of packing material and the drift eliminatormaterial comprises a first section of drift eliminator material, thesystem further comprising: a second section of packing material; and asecond section of drift eliminator material, wherein the first sectionof drift eliminator material is positioned between of the first sectionof packing material and the fan, and the second section of drifteliminator material is positioned between of the second section ofpacking material and the fan.
 20. The liquid-gas contacting system ofclaim 19, wherein the second section of drift eliminator material isattached to the second section of packing material.
 21. The liquid-gascontacting system of claim 11, wherein the dilute source comprises air.22. The liquid-gas contacting system of claim 11, wherein the pointsource comprises one or more of flue gas, reservoir gas, exhaust fluestack gases from power production equipment, exhaust flue stack gasesfrom concrete production equipment, or exhaust from combustionequipment.